X-ray apparatus.



W. D. COOLIDGE.

X-RAY APPARATUS. APPLICATION FILED "m1. m5. nguzwzn ocT. 243mm.

1,215,1 16. Patented Feb. 6,1917.

Inventor:

William llCoolidge HIS DIttgrfh'ey.

UNITED STATES PATENT OFFICE.

WILLIAM D. COOLIDGE, OF SCHENECTADY, NEW YORK,

ELECTRIC COMPANY, A CORPORATION OF ASSIC-NOR TO GENERAL NEW YORK.

X-RAY APPARATUS.

Application filed May 1, 1915, Serial No. 25,150.

To all whom it may concern:

Be it known that I, W ILLIA M D. Coomooic, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in X-R-ay Apparatus, of 'which the following is a specification.

The present invention comprises an X-ray device operable to yield a great output of Xra 's without overheating and melting the metal on the surface of the electrode subjected to the discharge.

It is well-known that one of the main limitations of X-ray tubes is the fact that the rapid evolution of heat at the focal spot causes the most refractory metals to melt locally even when the target has a large heat-storage capacity. In other Words, the 11 per limit of energy input is the value at w ich the heating effect of the cathode discharge at the focal spot melts and volatilizes the metal of the target.

In accordance with my invention, an X- ray tube of increased capacity is provided by rotating the tube as a whole and defiectmg the cathode beam out of line with the axis of rotation, thus renewing the surface subjected to the discharge while keeping the focal spot fixed in space.

The novel features of my invention will be pointed out with greater particularity in the appended claims, and for 'a'more de tailed description of the invention reference may be had to the accompanying drawings in which Figure 1 illustrates one embodiment of my invention partly in perspective and partly in section, and Fig. 2 a top view of the surface of the particular form of anode shown in Fig. 1. The particular X-ray tube illustrated is of the incandescent cathode type operating with a pure electron discharge as described by me in the Physical Review of December, 1913. The envelop 1 contains a cathode 2 adapted to be independently heated by passage of current, and an anode 3 consisting of refractory material, preferably tungsten. The cathode is surrounded by a concave focusing ring 4 which so modifies the electrostatic field as to cause the cathode rays to converge upon a spot of relatively small area on the surface of the anode. The tubular extensions 5, 6 of the envelop 1 are inserted in shafts 7, 8, mounted on bearings Specification of Letters Patent.

Pat ented Feb. 6, 1917.

Renewed October 24, 1916. Serial 'No. 127,498.

5), 10. These bearings are clamped to an insulating base plate 11 which is in turn connected to a shaft 12 surrounding the X-ray tube, consisting of lead glass or other material impervious to X-rays. Electrical connections are main nined to the cathode and anode by slip rings 13, 14, 15, the rings 13 and 1% serving ale) to convey a heating current to the cathode, which is indicated :is being furnished by a battery 16, connect ed in series with a resistance 17. The high potential current whic l generates the X-ray producing discharge is su apl'ied through conductors l8 and 19.

As described in the ibove mentioned article in the Pity steal Review the heating of the cathode to incandescence causes electrons to be emitted which travel under the influence of the im ressed electromotive force to the anode. Ihis cathode stream is diverted out of its axial position in the tube by means of a sole ioid 2O supplied With direct current by any suitable source, for example, a battery 21 in series with a resistance 22. The front of the anode 3 is preferablybut not necessarily of the shape of a truncated cone. lVhen the X-ray tube is revolved as by means of a belt 23, operating on a pulley whee 24, the cathodedischarge will be caused to travel in a circular path over the face of the anode while retaining its position 11 space so that the X-ray emitted may he used for photo graphic or any other purpose where focusing is desirable. As the metal receiving the cathode discharge is ;hus constantly renewed the energy capacity of the tube is correspondingly increas ad.

What I claim as new and desire to secure by Letters Patent of the United States, is 2- 1. An X-ray apparatus comprising the combination of an X-iay tube containing cooperating electrodes, means for rotating said tube, means for producing therein an X-ray generating cathode discharge, means for deflecting and holc'ing said discharge out of line with the axis of rotation of sa1d tube.

2. An X-ray apparatus comprising the combination of an X-r 21y tube, electrodes therefor, means for producing between said electrodes an X-ray g1 anerating electrical discharge, magnetic mi ans for deflecting said discharge to cause i; to impinge on the anode at a point removad from the center of rotation of said anode, and means for rotating said tube, whereby the bombarded area on said anode is renewed.-

3. An X-ray apparatus comprising the combination of an X-ray tube containing a cathode and an anode, means for rotating said tube, and means for holding fixed in space the cathode beam to focus on the anode at a point removed from the center of 10 rotation of said anode.

4. The combination of an X-ray device, 

